The substrate known per se comprises a transparent glass plate on which line-shaped, parallel transparent conductors are provided, which have a height of about 100 nm and which are made of Indium Tin Oxide (ITO) or other transparent, conductive material. Next, at right angles to the conductors, line-shaped, parallel, insulating shadowing structures have been applied, having a height of about 1-2 μm.
Thus, between the shadowing structures and the conducting paths, areas are formed having a length and a width of from 5 to some 400 μm. Optionally, on top of the transparent conducting paths and under the shadowing structures, a buffer layer may be provided, having a height of 0.5-5 μm, in which processes have boon provided within the areas mentioned earlier. The recesses extend to the depth of the conductor mentioned earlier, so that pits bounded on five side are formed. To make a polymer OLED display from the substrate, each area is to be filled with a polymer conductor (PDOT) and an organic electroluminescence medium (PPV). In a monochrome display a single type of PPV is deposited in all areas. A color display involves several types of PPV that emit different colors of light (for instance red, green and blue PPV). These types of PPV are to be deposited in different areas.
In the known method and apparatus for filling the areas of a substrate from which a display is being manufactured, use is made of an inkjet printhead which is movable relative to the table on which the substrate is accurately positioned. The table is provided with an electronic ruler, so that the position of the printhead relative to the table is known. In practice, it has been found that under the influence of various disturbing influences, such as, for instance, temperature variations in the substrate, an incorrect alignment of the substrate on the table and mechanical inaccuracies in the transport system of the table and/or the printhead, the liquid to be delivered by the printhead is not deposited in the areas on the substrate with sufficient accuracy (accuracies between 1/10 and 1/1000 of the length or width of the grain are desired). If any one of the areas of the substrate is not properly filled with liquid, such as, or instance, Pdot or red, green or blue PPV, the display will have to be rejected. It is therefore of essential importance that each area of the substrate can be accurately filled with the liquid. Especially when the substrates are greater, there is a substantial chance of defects owing to the disturbing influences mentioned earlier, such as temperature variations in the substrate, an incorrect alignment of the substrate on the table and mechanical inaccuracies in the transport system. To date, it has been attempted to tackle these problems by using a very accurate transport mechanism and very stable tables. However, practice has taught that these measures offer insufficient solace.